This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Nonalcoholic fatty liver disease (NAFLD) is a common and increasingly recognized disorder characterized by macrovesicular accumulation of fat in hepatocytes, usually found in association with obesity, insulin resistance, and hyperlipidemia. This condition occurs in both adults and children, and arguably represents the most common cause of liver disease in pre-adolescence and adolescence. Insulin resistance and oxidative stress are considered to be the two most important mechanisms in the pathogenesis of NAFLD. We hypothesize that metformin and vitamin E will lead to sustained reduction in serum ALT with biopsy proven NASH through changes in insulin resistance or oxidative stress. The principal objective of this randomized, multicenter, double-masked, placebo-controlled trial is to evaluate whether 96 weeks of treatment with either metformin of vitamin E leads to sustained reduction in serum ALT in nondiabetic children with NAFLD compared to treatment with placebo. In pediatric nondiabetic patients with Non-Alcoholic Fatty Liver Disease (NAFLD), improvement in insulin resistance over 96 weeks of treatment with metformin will result in sustained reduction in serum alanine aminotransferase (ALT) compared to treatment with placebo. In pediatric nondiabetic patients with NAFLD, improvement in oxidative stress status over 96 weeks of treatment with vitamin E will result in sustained reduction in serum ALT compared to treatment with placebo